- How much of a curve do you expect to see, at an altitude of 33km above a sphere of radius 6,371km?
- The timelapse video where the skies are all clear is probably intentionally edited together that way from different days with clear skies.
- Probably that "shadow" is just something on the lens in that footage?
- The airplanes, and their contrails, are mostly too small to see from space - they can turn into larger clouds in the right circumstances, but you can't accidentally, and probably if they are visible then that looks ugly and
- Other satellites are, similarly, too small to see, and most of them are over the horizon. One could probably intentionally capture footage of a satellite flyby from the ISS, but it wouldn't happen accidentally.
- The external cameras on the ISS are as much for filming bits of the ISS and the astronauts maintaining those bits (which the crew has to keep an eye on) as they are for watching the Earth underneath. Of course the view from the cameras is often obstructed.
- I'm going to say "video artifact" or "some debris floating off into space".
- Yeah duh they use harnesses a lot, moving around in zero-g relies 100% on grabbing onto stuff.
- You really should be able to tell the difference between something dipping below the horizon and something that's just very scaled-down due to distance.
- Did you consider looking up why the Blue Marble "has to be" photoshopped before acting as if it was damning? Look, satellites fly really high relative to, like, planes and mountains and stuff, but 100km altitude vs 6,371km radius is still way too low to get the whole Earth in-shot. High orbit is much more expensive. No-one's going to pay that kind of money just to get the real thing instead of the photoshop, you need to put a camera on some other big space mission, like the Apollo program that the original 1978 Blue Marble (which the modern photoshopped one is a remake of) was taken from.
- Okay, again with the finding the curve, I guess that was the title of the video - have you tried, like, building a 3d model Earth and looking around on the surface? Are you sure you're not just convincing yourself you should expect more visible curvature than the models actually predict?
- Well, yeah the curved paths turn flat when you change the projection, the fact that they're straight lines across the surface of a sphere was the point in the first place. But the thing about a circular map centred on the North Pole is, flights between two destinations in the Southern hemisphere are curved in opposite directions - there's not many big cities south of the equator, but look at e.g. Buenos Aires - Melbourne or something.
- Alternate explanation for why the Bali-los Angeles flight was suspiciously close to Alaska: the Air China flight connected through China instead of flying direct. Oh, look, it says right there in the news article you screencapped that the Bali-Los Angeles flight took off from Taiwan Taoyuan International Airport.
- Some of that balloon footage actually has some very visible curvature. Like the bit at 21:26 - put something flat under where the horizon meets the edges of the screen. It's curved.
- The relationship between density and buoyancy and gravity is well-studied in physics, your "density" explanation doesn't replace anything or add anything that's missing or even explain anything it just turns everything we already knew about density and buoyancy into nonsense by removing gravity from the equations.
- The four fundamental forces of the universe are gravity, electromagnetism, and the strong and weak nuclear forces. Those second two mainly effect the nuclei of atoms (hence the name), so to "show me something that's not a magnet that does this" is literally impossible. Asking for a kind of evidence that the theory you're arguing with says can't exist is a bit underhanded.
- A force that acts on things in proportion to their mass can be counteracted by a small force when it's acting on a small mass? Who would have guessed?
- The fact that a force that's supposed to be very weak except at large scales doesn't have any effects small-scale enough to be visible in everyday life or in experiments with everyday items is not much of an argument against that force being real.
- Okay, since you're making a big deal out of it I'll try to explain in more depth to wrap this up: The buoyancy in a helium balloon comes from the heavier air being pulled under the balloon by the influence of gravity, which pushes the balloon out of the way. That effect of gravity is the reason denser things sink and lighter things float. If you remove gravity from the explanation, density and buoyancy isn't a separate thing that you can use to explain why things fall, it's another of the things that just became mysteries because you destroyed the explanation for them.
I would add another curious fact about buoyancy. Inside an accelerating car, a helium balloon will move toward the front of the car, because the acceleration forward pushes the air toward the rear of the car, making it more dense on that side of the balloon. So the balloon "floats" on top of that denser air mass. Likewise, if you hit the brakes, the balloon moves to the back of the car, because now the air in the front is denser.
Incidentally, the similar effects of gravity and acceleration are what led Einstein to develop the General Theory of Relativity.